The present disclosure relates to a process and a system for the nondestructive determination of the quality of a weld seam. The present disclosure also relates to a welding device to produce a weld seam.
Various processes and systems for the nondestructive assessment of the quality of weld seams are known from prior art. During ultrasonic examinations, for example, acoustic pulses are sent through a weld seam of a component, whose resulting echoes are analyzed by way of a propagation time delay. Conclusions concerning the quality of the weld seam can also be drawn from measuring the geometry of weld seams. In particular, laser triangulation is used for this purpose. Additional known techniques are, for example, eddy current methods or the weld seam characterization by means of x-ray radiation.
The use of the above-mentioned quality control process depends on factors, such as the type of defect to be detected and the accessibility of the weld seam. Despite the diversity of known nondestructive checking methods, destructive control checking procedures frequently continue to be used.
The above-mentioned processes for determining the quality of weld seams have the disadvantage that they cannot be carried out during the welding process. Also, the time demand of these examining procedures is usually greater than the cycle time of the welded-together components, which makes a checking of each individual component almost impossible. In addition, not all types of defects can be detected by means of many of the above-mentioned methods. The information content of existing analyzing processes for characterizing weld seams generally lacks data concerning the so-called lack of fusion. Such a defect may occur even in the case of identical electric operating values of the welding control.
The present disclosure relates to a process and a system for the nondestructive determination of the quality of weld seams. The present disclosure also relates to a welding device by which the quality of the weld seams can be checked on each of the welded components without having to extend the cycle times.
The process for the nondestructive quality determination of weld seams comprises the process steps of: providing a first and a second component; connecting the first and second components by a weld seam produced by a welding operation; measuring a surface temperature of the weld seam and surface temperatures of areas of the first and second components adjacent to the weld seam that were heated by the welding operation; establishing a location-dependent profile from the measured surface temperature; and comparing the location-dependent profile with a desired profile. The system for carrying out the process for the non-destructive determination of the quality of a weld seam according to the above process steps comprises a measuring device to measure the surface temperatures and an analyzing unit to establish the location-dependent profiles and to compare the location-dependent profiles with the desired profile. The system also includes a welding device, wherein the welding device is a movable tool and the measuring device is movable at a constant distance behind the movable tool producing the weld seam.
When materials are joined by welding operations, energy in the form of heat is introduced into the surrounding material by way of the weld seam. The transfer of this heat into the surroundings of the weld seam can be observed by means of the surface temperature. The coupling-in or efficiency of the heat conduction is a direct function of weld seam parameters, such as the connection to the surrounding material, the position of the weld seam relative to the components to be joined as well as the initial gap measurement or the orientation of the components to be joined relative to one another. A quality determination of the weld seam can therefore be carried out in a reliable manner by the process according to the present disclosure. Information concerning fusion penetration, the most important parameter for the examination of a weld seam with respect to an existing lack of fusion, as well as information concerning root defects and through-burning can only by obtained in connection with the analysis of areas adjacent to a weld seam. Since, in addition, surface temperatures can be measured rapidly, all welded components can be subjected to a quality control, so that the risk of forwarding defective components resulting only from sampling can be excluded.
The temperature measuring takes place in a non-contact manner by detecting the emitted thermal radiation. Such non-contact temperature measuring is carried out by using a detector, such as an infrared camera having a detector, by which a rapid and reliable temperature measurement can be obtained. Matrix, line or individual detectors may be used.
The detection of the thermal radiation takes place by a heat radiation detecting detector which moves along the weld seam at the same speed as the tool producing the weld seam, such as a welding head. As a result, it is ensured that the same time difference exists for each point of the weld seam between its production and the temperature determination. A kinematic reversal, that is, an arrangement with a stationary welding head, a stationary detector and components passing through is also possible.
Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.